Exactly what I was going to say; it's a nutrient deficiency for sure. Especially red plants are quite demanding to stay that nice red coloration, iron will help boost its color. I've had similar issues in the past before with "holy" plants haha. My hygros are full of holes, even on super healthy...
I've actually been very successful at getting a carpeting plant started without the addition of co2. It was actually a mistake or actually a sign of neglect which gave me some of its success. I used to have tons of Dwarf Sagittaria (Sagittaria subulata) growing in my big tank until I went all...
I got rid of mine a long time ago, all I did was a bit of manual removal, cut down my photo period then turned the lights off for the weekend starting on Friday. When I came back on sunday night most of the remaining algae had turned brown and floated off.
http://www.aquariacentral.com/forums/showpost.php?p=2486123&postcount=42
I noticed great growth in just five days. But I do dose fertz, and have pressurized CO2.